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Background: With the advent of precision oncology, liquid biopsies are quickly gaining acceptance in the clinical setting. However, in some cases, the amount of DNA isolated is insufficient for Next-Generation Sequencing (NGS) analysis. The nCounter platform could be an alternative, but it has never been explored for detection of clinically relevant alterations in fluids., Methods: Circulating-free DNA (cfDNA) was purified from blood, cerebrospinal fluid, and ascites of patients with cancer and analyzed with the nCounter 3 D Single Nucleotide Variant (SNV) Solid Tumor Panel, which allows for detection of 97 driver mutations in 24 genes., Results: Validation experiments revealed that the nCounter SNV panel could detect mutations at allelic fractions of 0.02-2% in samples with ≥5 pg mutant DNA/µL. In a retrospective analysis of 70 cfDNAs from patients with cancer, the panel successfully detected EGFR, KRAS, BRAF, PIK3CA, and NRAS mutations when compared with previous genotyping in the same liquid biopsies and paired tumor tissues [Cohen kappa of 0.96 (CI = 0.92-1.00) and 0.90 (CI = 0.74-1.00), respectively]. In a prospective study including 91 liquid biopsies from patients with different malignancies, 90 yielded valid results with the SNV panel and mutations in EGFR, KRAS, BRAF, PIK3CA, TP53, NFE2L2, CTNNB1, ALK, FBXW7, and PTEN were found. Finally, serial liquid biopsies from a patient with NSCLC revealed that the semiquantitative results of the mutation analysis by the SNV panel correlated with the evolution of the disease., Conclusions: The nCounter platform requires less DNA than NGS and can be employed for routine mutation testing in liquid biopsies of patients with cancer., (© American Association for Clinical Chemistry 2021.)

Introduction: Collection of tumor samples is not always feasible in non-small cell lung cancer (NSCLC) patients, and circulating free DNA (cfDNA) extracted from blood represents a viable alternative. Different sensitive platforms have been developed for genetic cfDNA testing, some of which are already in clinical use. However, several difficulties remain, particularly the lack of standardization of these methodologies. Areas covered: Here, the authors present a review of the literature to update the applicability of cfDNA for diagnosis and monitoring of NSCLC patients. Expert commentary: Detection of somatic alterations in cfDNA is already in use in clinical practice and provides valuable information for patient management. Monitoring baseline alterations and emergence of resistance mutations is one of the most important clinical applications and can be used to non-invasively track disease evolution. Today, different technologies are available for cfDNA analysis, including whole-genome or exome sequencing and targeted methods that focus on a selection of genes of interest in a specific disease. In the case of Next Generation Sequencing (NGS) approaches, in depth coverage of candidate mutation loci can be achieved by selecting a limited number of targeted genes.

Many advanced cases of cancer show central nervous system, pleural, or peritoneal involvement. In this study, we prospectively analyzed if cerebrospinal fluid (CSF), pleural effusion (PE), and/or ascites (ASC) can be used to detect driver mutations and guide treatment decisions. We collected 42 CSF, PE, and ASC samples from advanced non‐small‐cell lung cancer and melanoma patients. Cell‐free DNA (cfDNA) was purified and driver mutations analyzed and quantified by PNA‐Q‐PCR or next‐generation sequencing. All 42 fluid samples were evaluable; clinically relevant mutations were detected in 41 (97.6%). Twenty‐three fluids had paired blood samples, 22 were mutation positive in fluid but only 14 in blood, and the abundance of the mutant alleles was significantly higher in fluids. Of the 34 fluids obtained at progression to different therapies, EGFR resistance mutations were detected in nine and ALK acquired mutations in two. The results of testing of CSF, PE, and ASC were used to guide treatment decisions, such as initiation of osimertinib treatment or selection of specific ALK tyrosine–kinase inhibitors. In conclusion, fluids close to metastatic sites are superior to blood for the detection of relevant mutations and can offer valuable clinical information, particularly in patients progressing to targeted therapies. [ABSTRACT FROM AUTHOR]